Incandescent electric lamp with base fuses



P 1942- A. M. HAGEMAN ETAL 2,295,652

INCANDESCENT ELECTRIC LAMP W ITH BASE FUSE Filed May 3, 1941 www- ATTORNEY Patented Sept. 15, 1942 INCANDESCENT ELECTRIC LAMP WITH BASE FUSES Aaron Martin Hageman, Verona,

and Paul Barringer Tully, Bloomfield, N. J., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application May 3, 1941, Serial No. 391,650

10 Claims.

This invention relates to incandescent electric lamps normally operated in series, and more particularly to a lamp having means incorporated therewith for permitting the current to by-pass upon failure of the lamp filament, and terminating the flow of said current if it increases beyond a predetermined point.

The principal object of our invention, generally considered, is to provide an incandescent electric lamp of the series type, such as may be used for Christmas tree decoration, and incorporate therein a basing cement which automatically becomes conducting upon failure of the filament and/or a fuse extending from one of the filament terminals to the base eyelet through a portion of said base not containing cement, said fuse being of such small cross section that it opens the circuit if the current therethrough increases beyond a predetermined point.

Another object of our invention is the provision of a base for a lamp of the series type, said base being connected to the lamp bulb by cement which terminates short of the eyelet, an insulator between the eyelet and base shell, and a fuse extending between said eyelet and a lead from the filament, said insulator being transparent so as to enable a party using said lamp to determine whether or not the fuse is burned out.

Other objects and advantages of the invention,

relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

Referring to the drawing:

Figure l is an enlarged elevational view, partly in axial section, of an incandescent electric lamp embodying our invention.

Figure 2 is a bottom plan view of the lamp shown in Figure 1.

Figure 3 is a view corresponding to Figure 2, but showing a modification.

Referring to the drawing in detail, like parts being designated by like reference characters, and first considering the embodiment of our invention illustrated in Figures 1 and 2, there is shown an incandescent electric lamp ill, of the series i type, comprising a bulb I l, and a conductive base shell [2 enclosing and secured to a portion of said bulb by cement I 3.

The lamp illustrated, is one of the type generally used for Christmas tree decoration and may i be burned in series with seven other similar lamps from a domestic lighting circuit of 110-120 volts, although we do not wish to be limited to this as more, such as twenty, or less may be connected in series.

vention, is so constructed that if the filament l4 breaks or burns out, the other lamps of the series continue to operate by virtue of the cement I3 only then becoming substantially conductive, as described and claimed in the concurrently filed application of E. R. Schmid, Serial No. 391,639, entitled Incandescent electric lamp and basing cement, and owned by the assignee of the present application. Essentially, the cement comprises an insulating binder such as shellac, Durite or Bakelite, a filler of finely divided conducting material such as aluminum, iron,

galena or graphite, and a solvent such as alcohol to make a paste.

If, however, enough of the lamps of the series burn out so that dangerous current surges occur in the conducting cord or string, provision is made for opening the circuit through the lamps, as will now be explained.

The preferably tungsten filament I4 is, in the present embodiment, supported upon a mount I5,

comprising lead-in conductors l6 and I1, passing;

through a glass bead l8, and with their inner ends secured to the ends of the filament, as indicated at [9 and 2|. The opposite ends of the conductors l6 and I1 pass through the portion 22 of the bulb which is embedded in the basing cement [3. The lead I1 passes through said cement and issecured, as by soldering, to the preferably brass base shell I 2, as indicated at 23. The other lead l6 passes through the portion 22 of the lamp bulb into the basing cement l3, and instead of continuing to the base eyelet 24, insulated from theconducting or brass shell 12 by means of a black glass insulator 25 in accordance with the usual practice, has secured or crimped thereto, one end of a fuse device 26, the other end of said device being secured or soldered to said eyelet or central contact 24, as indicated at 21.

The fuse device 26, if used with an ordinary Christmas tree lamp in series with seven other similar lamps on a domestic lighting circuit, desirably is formed of 4 mil nickel or iron wire not less than 10 mm. in length. Such fine wire acts as a fuse, in that it melts and opens the circuit when current of from one-half to ten amperes flows through the string and prevents high current surges which, with the particular kind of basing cement used in such shortcircuiting lamps, would cause some fire hazard.

The fuse may be attached to the eyelet lead by any of several methods, the only requirement being that it is securely fastened and at least long enough and of such size and material that it will The lamp in accordance with our in- 55 open the circuit without dangerous arcing if current surges in excess of one ampere occur. It is, therefore, essential that the basing cement l3 occupy only the bulb-adjacent portion of the base shell cavity and leave enough vacant or arcstopping space adjacent the eyelet or contact 24 to receive a long enough fuse wire.

Referring now to the embodiment of our invention illustrated in Figure 3, there is shown a lamp m which may be of a construction identical with that of the lamp of the preceding embodiment, except that the insulator 25 is made of clear glass so that the fuse device in the base, corresponding with the device 26 of the preceding embodiment, is visible so it may be readily determined whether or not said device is intact.

From the foregoing, it will be seen that we have devised a lamp of the series type which maintains other lamps of the string operating even after failure of its filament by short-circuiting basing cement which becomes substantially conducting only under such circumstances, while, at the same time, fire hazard is avoided by means for breaking the circuit therethrough if the current through the string of lamps becomes excessive.

Although preferred embodiments of our invenvariation may be accompanied by a corresponding variation of another feature or features, if considered desirable. Therefore, modifications may be made within the spirit and scope of the appended claims.

We claim:

1. An incandescent electric lamp comprising a bulb, a filament disposed in said bulb and lead wires projecting therefrom, a base including a conducting shell rece ving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb, securing said parts together, and terminating short of said contact member, leaving an effective arc-stopping space thcrebetween, one of said leads being connected to said shell and the other embedded in said cement and terminating short of said contact member, and fused means passing through said space and connecting said last-mentioned lead to said contact member.

2. An incandescent electric lamp comprising a bulb, a filament disposed in said bulb and lead wires projecting therefrom, a base including a conducting shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb, securing said parts together, and terminating short of said contact member, leaving an effective arc-stopping space therebetween, one of said leads being connected to said shell and the other embedded in said cement and terminating short of said contact member, and a wire of less carrying capacity than one of said leads passing through said space and connecting said lastmentioned lead to said contact member.

3. A series Christmas tree incandescent electric lamp comprising a bulb, a filament disposed in said bulb and lead wires projecting therefrom, a base including a conducting shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb, securing said parts together, and terminating short of said contact member, leaving an effective arc-stopping space therebetween, one of said leads being connected to said shell and the other embedded in said cement and terminating short of said contact member, and a four mil fuse wire passing through said space and connecting said last-mentioned lead to said contact member.

4. An incandescent electric lamp comprising a bulb, a mount with a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement being capable of serving as an insulator during the normal operation of the lamp and as a conductor upon the failure of said filament and terminating short of said contact member so as to leave an effective arc-stopping space therebetween, one of said leads being embedded in said cement and connected to said shell, the other embedded in said cement and ter-- minating short of said contact member, and a fuse connecting said last-mentioned lead to said contact member and passing through said space.

5. An incandescent electric lamp comprising a bulb, a mount with a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement being capable of serving as an insulator during the normal operation of the lamp and as a conductor upon the failure of said filament and terminating short of said contact member so as to leave an effective arc-stopping space threebetween, one of said leads being embedded in said cement and connected to said shell, the other embedded in said cement and terminating short of said contact member, and a wire of less carrying capacity than one of said leads connecting said last-mentioned lead to said contact member and passing through said space.

6. An incandescent electric lamp of the Christmas tree series type, comprising a bulb, a mount with a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement being of such a composition that it acts as an insulator when normal voltage is impressed on said lamp, and as a conductor if abnormally high voltage is impressed thereon and terminating short of said contact member so as to leave a space therebetween, one of said leads being connected to said shell and the other embedded in said cement and connected to said contact member by means acting as a fuse and passing through said space.

7. A series Christmas tree incandescent electric lamp comprising a bulb, a mount with a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement being capable of serving as an insulator during the normal operation of the lamp and as a conductor upon the failure of said filament and terminating short of said contact member so as to leave an effective arc-stopping space therebetween, one of said leads being embedded in said cement and connected to said shell, the other embedded in said cement and terminating short of said contact member, and four mil fuse wire connecting said last-mentioned lead to said contact member and passing through said space.

8. An incandescent electric lamp comprising a bulb, a mount with a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member insulated from said shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement comprising an insulating binder and a finely divided conducting filler mixed in such proportions that it is adapted to conduct no appreciable current when said lamp is in a series string with the other lamps operating, so that only its proportion of the applied voltage is impressed thereon, and as a conductor if its filament burns out and an abnormally large proportion of the applied voltage is impressed thereon, and terminating short of said contact member so as to leave an efiective arcstopping space therebetween, one of said leads being embedded in said cement and connected to said shell and the other embedded in said cement and terminating short of said contact member, and a fuse connecting said last-mentioned lead to said contact member and passing through said space. i

9. An incandescent electric lamp comprising a bulb, a filament disposed in said bulb and lead wires projecting therefrom, a base including a conducting shell receiving a portion of said bulb,

a contact member, insulation between said contact member and shell, basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing the parts together and terminating short of said contact member leaving an effective arc-stopping space therebetween, one of said leads being connected to said shell and the other embedded in said cement and terminating short of said contact member, and a fuse wire passing through said space and connecting said last-mentioned lead to said contact member, said contact member insulator being transparent to show the condition of said fuse wire.

10. An incandescent electric lamp comprising a bulb, a filament disposed in said bulb and lead wires projecting therefrom, a base including a metallic shell receiving a portion of said bulb, a contact member, transparent insulation material between said contact member and shell, basing cement disposed between the peripheral portion of said shell and th received portion of said bulb for securing said parts together, said cement comprising an insulating binder and a finely divided conducting filler mixed in such proportions that it conducts no appreciable current when said lamp is operating with other lamps in a series string so that oniy its proportion of the applied voltage is impressed thereon and as a conductor if the filament burns out or an abnormally large proportion of the applied voltage is impressed thereon and terminating short of said contact member so as to leave an effective arestopping space therebetween, one of said leads being embedded in said cement and terminating short of said contact member, and a fuse connecting said lead to said contact member and passing through said space.

AARON MARTIN HAGEMAN. PAUL BARRINGER TULLY. 

